Assignment-1-Part-3

Solution

programming-with-r/assignments/assignment-1-air-pollution/corr.R

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+corr <- function(directory, threshold = 0) {
+  ## 'directory' is a character vector of length 1 indicating
+  ## the location of the CSV files
+
+  ## 'threshold' is a numeric vector of length 1 indicating the
+  ## number of completely observed observations (on all
+  ## variables) required to compute the correlation between
+  ## nitrate and sulfate; the default is 0
+
+  ## Return a numeric vector of correlations
+  source("complete.R")
+  completeCases <- complete(directory)
+  casesAboveThreshold <- completeCases[completeCases$nobs > threshold,1]
+  allFiles <- list.files(path = directory, full.names = TRUE)
+  correlations <- rep(NA,length(casesAboveThreshold))
+  for (i in casesAboveThreshold) {
+    fileData <- (read.csv(allFiles[i]))
+    completeCases <- complete.cases(fileData)
+    validSulfateData <- fileData[completeCases, 2]
+    validNitrateData <- fileData[completeCases, 3]
+    correlations[i] <- cor(x = validSulfateData, y = validNitrateData)
+    #print(head(fileData[completeCases,]))
+    #print(validSulfateData)
+    #print(validNitrateData)
+  }
+  correlations <- correlations[complete.cases(correlations)]
+}